Hi shuanc,
Welcome to PCHF.
If it's coming up with a password screen, then somebody would have needed to create a password in order for it to ask for it.
Luckey enough, you should be able to reset this password by opening up the PC, and removing the battery for a short while. Depending on your PC model, this battery should be on the corner of the motherboard, shown as BTY on this diagram:
